The present invention relates to a gas channel forming plate for a fuel cell that is arranged between a membrane electrode assembly and a separator plate, and to a fuel cell stack formed by stacking a plurality of single cells.
For example, a solid polymer electrolyte fuel cell includes a fuel cell stack formed by stacking a plurality of single cells each having a structure in which a membrane electrode assembly is sandwiched between a pair of separators.
One type of such separators includes a flat separator plate and a gas channel forming plate arranged between the flat separator plate and a membrane electrode assembly (for example, Japanese Laid-Open Patent Publication No. 2014-167860).
The gas channel forming plate described in the publication has grooves in the surface that faces the membrane electrode assembly. The grooves are arranged at intervals. The grooves function as gas channels through which gas (fuel gas and oxidant gas) supplied to the interior of the single cell (specifically, the membrane electrode assembly) flows. The gas channel forming plate has protrusions each arranged between adjacent gas channels, and the protrusions form grooves on the back side. These grooves function as water channels for discharging water generated inside the single cell during power generation to the outside of the single cell. Further, each protrusion has through holes (communication passages) for connecting the gas channels and the water channels to each other.
In such a fuel cell stack, water generated during power generation at the membrane electrode assembly flows into the water channels via the communication passages of the gas channel forming plate. The water that has flowed into the water channels is carried away by the dynamic pressure of the gas flowing inside the water channels and is discharged to the outside of the water channels.
The above-described gas channel forming plate has a structure capable of draining water to the water channels only in sections where the communication passages are formed. Therefore, although water generated in the vicinity of the communication passages is promptly discharged to the water channels, water generated at sections distant from the communication passages takes time to be discharged to the water channels.